Carrion Crows Can Volitionally Control Their Calls, Researchers Say
Carrion crows (Corvus corone), a species of songbird in the family of Corvidae, can voluntarily control the release and onset of their calls, suggesting that songbird calls are under cognitive control, according to new research from the University of Tübingen, Germany.
Songbirds are renowned for their acoustically elaborate songs, which show a degree of flexibility, potentially indicating that they are under conscious control.
However, the observed variability in vocalizations might simply be driven by involuntary mechanisms, and need not be based on cognitive control.
In the study, Katharina Brecht and her colleagues at the University of Tübingen tested the idea that songbirds deliberately control their calls, in the sense that they can be emitted or inhibited at will, as opposed to being knee-jerk responses to food, mates, or predators.
Their findings show that trained carrion crows can exert control over their calls in a goal-directed manner.
In a detection task, three male carrion crows rapidly learned to emit calls in response to a visual cue (colored squares) with no inherent meaning (go-trials), and to withhold calls in response to another cue.
Two of the birds were then trained on a task with the cue colors reversed, in addition to being rewarded for withholding vocalizations to yet another cue (nogo-trials).
Vocalizations in response to the detection of the go-cue were precise timed and highly reliable in all three crows.
The crows also quickly learned to withhold calls in nogo-trials, showing that vocalizations weren’t produced by an anticipation of a food reward in correct trials.
“Our study shows that crows can be taught to control their vocalizations, just like primates can, and that their vocalizations are not just a reflexive response,” the researchers said.
“This finding not only demonstrates once again the cognitive sophistication of the birds of the crow family.”
“It also advances our understanding of the evolution of vocal control.”
The team’s paper was published in the journal PLoS Biology.
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K.F. Brecht et al. 2019. Volitional control of vocalizations in corvid songbirds. PLoS Biol 17 (8): e3000375; doi: 10.1371/journal.pbio.3000375